https://www.gamespot.com/articles/gta-5-online-transform-races-new-weekly-update-out/1100-6454138/

Rockstar has revealed the new content in store for Grand Theft Auto V this week. Along with the usual batch of discounts and rewards, the biggest addition to GTA Online is the much-anticipated Transform Races, a new Stunt Race mode that players can participate in starting today.

During the course of a Transform Race, your vehicle will change between bikes, cars, planes, and more depending on the terrain. The transformation happens automatically when you reach a certain point in the track. Transform Races also introduce a new type of checkpoint called Warps, which will instantly transport you to a different location on the map.